Method and apparatus for treating plastic film



April 10, 1945. H. 1 YOUNG METHOD AND APPARATUS FOR TREATING PLASTICFILM Filed March 5, 1943 Patented Apr. l0, 1945 *UNITED STATES [PATENTloFFl-CE ME'rrIoD AND APPARATUS ron TREATING PLASTIC lFILM Harvey L.Young, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N.Y., a corporation of New York Application March 3, 1943, Serial No.477,847

' 16 claims. (of. 1s'1) This invention relates to the treatment of filmsof heat plastic material and is especially useful in shrinking ofcalendered films of plastic ma'- terial.

In the manufacture of films ofv thermoplastic material such asplasticized polymerized vinyl chloride by calendering the film from abatch of the material it has been found that a molecular stretchingapparently takes place so that the material after calendering is underlongitudinal stress and shrinks lengthwise with a corresponding wideningof the flhn under heat treatment.

It has also been found that when it is attemptedA to remove the stressby heat applied thereto the `material becomes so adhesive as to prohibitthe use of heat conducting means applied directly ,to its surface whileheat applied by radiation flrst causes the film to buckle or wrinkle soas to defeat uniform heating thereafter and the sticky nature of theheated material makes tentering of tion, parts being broken away to show the mech anism.

Fig.'2 isa vertical sectional view taken on line 2-2 of Fig. 1, partsbeing broken away.

Fig. 3 is a sectional plan view taken on line l 3-3 of Fig. 1, partsbeing broken away.

Fig. A4 is a detail sectional plan view taken on line 4-4 of Fig. 1-. f

In the illustrated embodiment of the invention a film of calenderedplastic is fedl downwardly between adjustable heat--radiieiting` meansinto a tank of cooling liquid and between spread'ng means designedtoflatten the film. The nim travels from a vertical to a horizontalposition about a -set of spreading rollers constructed andarrangedsothat the film 'is positively. driven thereby and is furthercooled by passing horizontally to a submerged roller about which itturns'to 4 emerge from the tank.

Referring lto the drawing, a cooling tank I6, open at its top, issupported by columns Il. li', i2, I2 and is provided with an inlet pipei 3 for siipplying cooling water, and an outlet pipe i4. Fixed totheside walls of the tank and extending thereabove are brackets I5, i6, I1,I8. Brackets i5, I6 at one side of the tank have aligned bearings I9,vfor rotatably supporting a shaft and brackets Il, i8 are similarlyformed with aligned bearings for a similar shaft 26 parallel thereto.These shafts have sprockets 2l, 28 fixed thereto respectively and achain 2.9 extends about these sprockets to move them in unison. Ahandwheel 30 is xed to shaft 25 to turn the shafts. A carriage hasthreaded engagement with right-hand threads of shafts 25, 26 and asimilar carriage 36 has threaded engagement with lefthand threads of thesame shafts. These carriages are in the form of reflectors facing eachother 30 bers.

yand the counter-shaft respectively.

and supporting heating elements 3l preferably adapted to be heated byelectricity. The arrangement is such that a film 40 may be passedVvertically into the tank between the heating elements which may beadjusted toward and awa from the film.

For feeding the film to the tank, columns 45, 45 are provided and spacedfrom frame members ii, il' by frame members 46, 46. A roll 4l of the nlm40 is supported for rotation in chocks 48, 48', supported by columns 45,45 and is led about an idler roll 49 and then about driven rolls 50, 5|rotatably journaled on the frame mem- A weighted idler roll 52 isJournaled in a swing frame 53 hinged to the frame members so as to reston the film over roll to increase the frictional driving thereof. Asimilar idler roll 54 is journaled in a swing frame 55.

An electric motor 6i) drives a speed reducer lSII -which in turn drivesa variable speed drive 62 of the Reeves type,which in turn drives acounter-shaft .63 rotatably journaled in the frame members 46, 46through a chain 64 and sprockets fixed to the driving shaft of the speedreducer Countershaft 63 in turn drives rolls 50, 6I through chains 65,66 and sprockets fixed to the shafts. 'Rolls 50 and 5| are driven at thesame speed. The arrangement is such that the delivery speed of roll 5Imay be adjusted to regulate the speed of the nlm passing between theheating elements.

As the nlm is Iheated it softens and' tends to buckle due to shrinkageso as to drape in folds. The folds, if allowed to develop freely, wouldshield some portions from the heat and disturb the uniformity ofdistance between the heating v elements and the film, causing unevenheating.

To prevent undesirable buckling and draping.

a set of discs 1 0 are mounted submerged in the cooling liquid forrotation about axes in the same vertical plane with their axes inclinedprogressively to the horizontal from the center line of the filmoutwardly toward its margins and with the tops of the rollers tangent tothe same horizontal plane. The discs are individually mounted in forks1| having cylindrical Shanks 12 clamped in horizontal apertures of a.bar 13 fixed to the tank, and are adjusted so as to rotate in divergingdirections in respect to the I direction of the film. The forks areclamped in place by set screws 14. Each disc has a rubberfaced peripheryto provide better traction.

For driving the discs, a roller 15 is rotatably mounted in bearings 16,11 secured to the tank with its axis in the same vertical plane as thediscs and its periphery tangent to the discs. The roll 15 has itssurface friction increased as by a coveringy of friction tape toincrease traction. Bearings 1S, 11 are adjustable vertically inguideways 18, 19 and are locked in place by set screws. A pulley 80 isfixed to roller 15 for driving it.

For pressing the film against discs 10, a carriage 85 is slidablymounted in a horizontal guideway of a plate 86 fixed to the tank bottom.A 'second set of discs 81 are individually mounted for rotation in forks88 having cylindrical shanks 89 rotatably mounted in horizontalapertures in carriage 85 and clamped in place by set screws 90. Eachdisc 81 is opposite a disc 10 and is adjusted to rotate in the sameplane as its mate. Pressure between the pairs of discs is applied bysprings 95, 96 which urge the carriage 85 toward the bar 13.

For releasing the spring pressure on the discs for threading themachine, carriage 85 has ears 91, 98 on its ends. Ears 99, |00 are fixedto the tank in line therewith, and rods |02 are passed through the ears.The springs 95, 96 are mounted about the rods between ears 91, 98respectively and stop collars on the ends of rods |0|, |02 respectively.The rods have collars |09, |04 fixed to their opposite ends. Thesecollars have inclined cam faces which me' Between 'rens los and las. ncomprises av series of short rollers |28 mounted for free rotation abouta bar |29 which is bowed convexly toward roll |09. Its rolls rotate bycontact with the film and in divergent directions to spread or tenterthe film.y contacting therewith.

For driving roll 15, a countershaft |30 is rotatably mounted on the tanki0 and is driven from countershaft ||0 by a chain |3| and suitablesprockets. Shaft |30 has a pulley |32 fixed thereto which drives rollerthrough a belt |38 engaging pulley 80.

In the operation of the apparatus a. roll 41 of calendered film isplaced in chocks 48, 48 and threaded about roll 49 between rolls 80 and52, and between rolls 5| and 54, rolls 50 and 5| ywithdrawing the film;from roll 41 at a uniform speed adjustable by virtue of the variablespeed film by energizing the heating elements 81 and the machine isready for operation. The speed of the discs 10 and the winding speed ofthe film will vary with adjustment of the variable speed drive 62 butmay be v ried with respect to speed of delivery of the film by virtue ofvariable speed drive H2. Variable speed drive ||2 is adjusted so thatthe withdrawal speed is less than the feed-in speed by the amount toengage cam faces on ears 99, |00. The arrangement is such that byrotating the rods |0|, |02

in one direction the springs 95, 98 are placed under compression, and byrotating them in the opposite direction the spring pressure is released.

is rotatably mounted on columns I2, I2'. A.

similar rubber covered driven roller |09 is rotatably mounted on framemembers |06, |86'. A countershaft ||8 is rotatably mounted on co1- umnsI2, l2' and is driven by a chain and suitable sprockets from a variablespeed drive ||2 which in turn is driven by variable speed drive 82.Chain drives H8, ||4, drive rolls |08, |09 respectively from.countershaftiiii. A-set of chocks |20, |20' are fixed to frame members|06, |06' and have vertical slots for retaining a shaft |2| about whicha stock shell |22 is rotatably carried. Stock shell |22 receives thefilm which is rewound thereon by contact with driven roll I 09 and isrewound at the surface speed of roll |09. A weighted roll |28 isrotatably accommodate shrinkage and .the angular disposition of discs10, 81 is adjusted to tenter the film by an amount corresponding to thewidening of the film due to shrinkage.

As the discs 10, 81 are submerged in water or other cooling liquid whichis not a solvent of the film, and the film is wet by the liquid beforeit contacts the discs, the fllm does not adhere tofthe discs althoughthe discs are effective to remove buckles and wrinkles extending abovethe liquid where the film is extremely adhesive. The water or otherliquid also cools and sets the plastic film.

The heating means are adjustable as to dise i tance from the film, eventhough it may heat from the scope of the invention as it isC defined bythe film to as much as 300 F'. so that the water in the tank is raisedto boiling temperature at the position of immersion of the film, yet itis found that the apparatus effectively accomplishes the purposeshereinbefore stated. Water may be admitted and circulated to maintainthe water in the tank' at the desired temper atures. v

Variations may be made without departing the following claims.

I claim: l. Apparatus for treating a film of thermoplastic material,said apparatus comprisings from an intermediate region of thev film.

mounted in a swing frame |28 hinged to columns |2, I2' and rests on thefilm over roll |08 to increase traction. A spreading roll |21 (shown inFig. 4) is mounted on frame members |88,

I" for conducting a heated` film progressively into 2. Apparatus fortreating a film of material which tends to wrinkle when heated, saidapperatus comprising a bath of cooling liquid, means said lbath, andmeans for stretching the fllm laterally while drawing the nlm into saidbath.

3. Apparatus for treating a nlm` of thermoplastic material, saidapparatus comprising a bath of cooling liquid, means for conducting aheated ilim progressively into said bath, means for withdrawing the filmfrom the bath at a speed reduced to compensate for longitudinalshrinkage, and means submerged in the bath for stretching the filmlaterally.

4. Apparatus for treating a iilm of thermoplastic material, saidapparatus comprising a bath` of cooling liquid, means for conducting afilm progressively into said bath, means for progressively heatingthefilm as it approaches the bath, and means submerged in the bath forstretching the film laterally.

5. Apparatus for treating a film of material which tends to wrinkle whenheated, said apparatus comprising a bath of cooling liquid, means forconducting a film progressively through a free reach thereof into saidbath, means for progressively heating said reach, and means submerged inthe bath for stretching the film laterally in said reach.

6. Apparatus for treating a nlm of thermoplastic material, saidapparatus comprisingl a bath of cooling liquid, means for conducting afilm progressively through a free reach thereof into said bath, meansfor progressively heating said film in said reach, and means submergedin the bath for stretching the film laterally above the bath in saidreach..

7. Apparatus for treating a film of thermoplastic material, saidapparatus comprising a bath of cooling liquid, means for conducting afree reach of the film into said bath, heatasra'ais free reach thereofat a reduced speed tocompensate for longitudinal shrinkage, and meansfor stretching the film in said reach to take up lateral expansion dueto shrinking.

1l. Apparatus for treating a film of thermoplastic material which tendsto buckle when heated, said apparatus comprising a bath .of

. cooling liquid, means for advancing the nlm progressively into a freereach thereof extending into said bath, radiating means for heating thefilm at the free reach thereof to shrink the a reduced speed tocompensate for longitudinal radiating means at opposite sides of saidreach I for heating it as it'passes to said bath, and means submerged insaid bath for stretching thefllrnl laterally to prevent excessivebuckling of the heated fum above seid bath.

8. Apparatus for treating a film of material which tends to wrinkle whenheated. said'apparatus comprising cooling means, means for conducting aheated film progressively to said means, cooperating pairs of rotatablediscs for engaging the film at positions across its width for advancingthe film through said cooling means, said discs being inclinedprogressively from the center v to the edges of the film in divergingrelation to the `direction of travel of the nlm to spread the filmlaterally. and means for rotating at least some of the discs to advancethe film.

9-.Apparatus'for treating a film of thermo# plastic material, saidapparatus comprising a bath of cooling liquid, means for conducting afree reach of heated nlm to said bath, cooperating pairs of rotatablediscs submerged'in said bath for engaging the film at positions. acrossits width, said discs being inclined progressively from the center tothe edges of the nlm in diverging relation to the direction of travel ofthelm to spreadthe nlm laterally, and means for rotat-4 ing at leastsome ofthe discs through said bath.

10. Apparatus for treating a film of thermoplastic material, saidapparatus comprising delivery means for progressively ladvancing thefilm into a free reach thereof, radiating means toadvance the film forheating the film at the free reach thereofto shrink the nlm lengthwise,means engaging thenlmataspeedslowerthanthat of the delivery means forwithdrawing the nlm .from the' shrinkage, and means submerged in saidbath for v stretching the film to take up lateral expansion due toshrinkage, aaid last-named means being effective to prevent excessivebuckling in said free reach above said bath.

l2. Apparatus for treating a film of thermoplastic material, saidapparatus comprising a bath of' cooling liquid, means for advancing thenlm progressively into a 'free reach thereof extending into said bath,radiating means for heating the film at the free reach thereof to shrinkthe film lengthwise, means for withdrawing the film through said bathfrom the free reach thereof at a reduced speed to compensate forlongitudinal` shrinkage, and means submerged in saidA bath for spreadingthe nlm to take up lateral expansion due to shrinkage, said last-namedmeans being edective to prevent excessiv buckling in said free reachabove said bath, said spreading means 'comprising pairs of rotatablediscs for engaging the film at positions across the illm, said discsbeing inclined progressively from the center of the nlm toward its edgesin a direction diverging with respect to the direction of travel of thefilm.

13. The method of treating a nlm of material which tends to wrinkle whenheatedr which comprises feeding the film progressively to a free reachthereof, advancing the nlm from the free reach through cooling means,and stretching the film laterally of its direction of travel in saidreach as it approaches the cooling means. y

i4. The method .of treating a film of thermoplastic material which tendsto wrinkle when heated. which comprises progressively heating the film,feedingthe heated nlm downwardly into a bath of cooling liquid, andstretching the nlm above said bath to compensate for longitudinal`tudlnal shrinkage while drawing the nlm shrinkage thereof.

l5. The method of treating plastic material which tends to wrinkle whenheated which comprises progressively feeding the film downwardly to abath of-coollng liquid in a lfree reach, heating the film at the freereach,

and stretching the nlm above said bath and at a submerged position to,compensate for lozugithrough the bath at a reduced speed.

16. The method of treating a nlm plastic material which rends to"wrinkle when Ymergedpositlon toremovo excessive bucklingin heated whichcomprises vely feeding the heated film downwardlythrough a free reachintoabethofcoolingliquid. ing 'the nlm in said reach, throughthebathatareduced speed-tocompensate for' longitudinal shrinkage, andstretching thelmlaterallyabovesaidbathandatasubthe said free reach andto compensate for lateral expansion due to longitudinal p HARVEY L.YDUNG'.

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